Sen. Hubert H. Humphrey (D-Minn.) and Health, Education and Welfare Secretary Joseph A. Califano Jr. are old friends. And one night early in December, they both watched the same television show - the CBS program "60 Minutes."

Had it not been for that, Califano might never have called a news conference, as he did yesterday, to endorse enthusiastically an effort by the Rev. Jesse Jackson of Chicago aimed at motivating disadvantaged children to buckle down and study.

Califano was clearly moved yesterday as, with Jackson seated beside him, he announced two grants totaling $45,000 to study Jackson's PUSH for Excellence, Inc., Program, now operating in Los Angeles, Chicago and Kansas City, and to finance a Howard University conference May 17 to look for ways of expanding its operation.

And he hinted strongly that if the study shows Jackson has found a way to motivate kids - as Califano believes he has - there will be considerably more federal money going into PUSH for Excellence.

Califano abandoned his usual practice of reading a prepared statement during the unusually long, hour-and-a-half news conference.

"I'd really like to talk personally for a little bit, because this all happened very personally . . ." he said.

"I was watching television, the CBS broadcast '60 Minutes,' on a Sunday night a few weeks ago . . . I had not really seen or talked to Jesse since the 1960s, when I think he was at the White House to see President Johnson . . ." The broadcast featured a report on Jackson's program.

"I was very impressed by that broadcast. A couple of nights later . . . Hubert Humphrey called me and said he had seen the same broadcast, that he had talked to Reverend Jackson, and that he thought this project made a lot of sense. He thought HEW should invest some of its resources into this kind of a project, and would I please see him [Jackson]."

Califano then called Jackson, who, quite unknown to the secretary, had been negotiating with others in HEW to see if the federal government would support his program.

Califano said HEW took a closer look at the program before making a decision, including checking with Los Angeles Mayor Thomas Bradley.

The secretary called the program "tremendous . . . It's apparent that for whatever reason in whatever way . . . these students seem to be motivated . . . Their parents have become involved with their individual children, and they are learning."

Jackson tried for 18 months to launch the program here in the District, without success.

He described it yesterday as an attempt to bring youngsters, their parents, their teachers, their principals and their church leaders together in a cooperative pledge to see to it that homework and studying get done.

". . . I'm here to argue today that it is not for soulful reasons that we develop great athletes, but for very scientific reasons," Jackson said.

"They practice an average of three hours a day without radio, television and telephone. And whatever people do most and do much, they do well. If we apply three hours of uninterrupted time at night or in the afternoon to reading and writing and counting, our cognitive skills will be as great as are our motor skills."

There are other aspects to Jackson's program.

"We will not in the name of permissive liberalism try to justify smoking marijuana, or talk about how [harmless] angle dust is . . . or try to rationalize premature pregnancy, or try to deal past a young man's responsibility for a sexual relationship using abortion as a quick way out.

"We contend that fundamental responsibility and self-reliance is critical to people's survival . . . We tell our children that its not your aptitude but your attitude that determines your altitude with a little intestinal fortitude."

Califano nodded approvingly as Jackson, who sported a big "Excel" button on his lapel, talked on.

"All thevjnstincts . . . made me think this was a very worthwhile and important project," the secretary said. "While I'm Secretary of HEW, I would like as much as anything else to make some significant contribution to children learning the basic skills, to children wanting to be excellent in the schoolroom."

Jackson said the money represents the first major grant ever received by PUSH for Excellence, which has been funded primarily by the cities in which it operates, and Ford Foundation grants.